CN110076754B - Mobile parallel mechanism with multiple motion modes and control method thereof - Google Patents

Abstract

The invention belongs to the technical field of motion control, and discloses a moving parallel mechanism with multiple motion modes, comprising an upper platform and a lower platform in a parallelogram structure, the upper platform and the lower platform are arranged in parallel, and a plurality of Branch chains, a plurality of the branch chains are arranged in parallel with each other, including three rotating pairs and one moving pair, the head and tail ends of which are connected with the upper platform and the lower platform through the steering gear, and the axial centerlines of the rotating shafts of all the rotating pairs They are all parallel to each other and parallel to the same side of the upper or lower platform. Also disclosed is a control method for a moving parallel mechanism in a multi-movement mode. The rotation of the corresponding first rotation pair and the second rotation pair is controlled by a plurality of the steering gears, and the rotation of the corresponding third rotation pair is driven, thereby controlling the rotation of the corresponding third rotation pair. The corresponding branch chain is continuously bent and straightened to realize the alternate landing of the upper platform and the lower platform, thereby realizing the rolling mode of the mobile parallel mechanism.

Description

A kind of moving parallel mechanism with multi-motion mode and its control method

technical field

The present invention relates to the technical field of motion control, and in particular, to a moving parallel mechanism with multiple motion modes and a control method thereof.

Background technique

With the development of robots, mobile robots have been used in many fields, such as rescue and disaster relief, space exploration, military reconnaissance, and autonomous operation tasks such as autonomous detonation. Therefore, the multi-mode mobile mechanism is the demand for the development of today's mobile robots.

At present, a mechanism that integrates and switches a variety of moving methods such as full-position rolling and four-legged walking on the same mechanism, such as the "Danti" eight-legged walking robot funded by NASA in the United States, and a four-legged walking robot developed by Boston Dynamics Robot BigDog, although the above robots have multiple motion modes, they realize multi-motion modes in a modular self-reconfiguration method, which has the disadvantages of complex control, insufficient stiffness, insufficient precision, and poor stability. In addition, due to the characteristics of high stiffness, high precision, large bearing capacity and its inherent properties of parallel mechanisms, there are few studies on their application in multi-mode moving mechanisms. Therefore, the development of a multi-mode step with good stiffness and simple control Rolling and moving parallel mechanism is of great practical significance.

SUMMARY OF THE INVENTION

The invention provides a multi-movement mode mobile parallel mechanism and a control method, and solves the problems of the existing multi-movement mode robot, such as complex control, insufficient rigidity, precision and poor stability.

The present invention can be realized through the following technical solutions:

A moving parallel mechanism with multi-movement mode, comprising an upper platform and a lower platform of a parallelogram structure, the upper platform and the lower platform are arranged in parallel, a plurality of branch chains are arranged between the two, and the plurality of the branch chains are parallel to each other Set, including three rotating pairs and one moving pair, the head and tail ends of which are connected to the upper platform and the lower platform through the steering gear, and the axial centerlines of the rotating shafts of all the rotating pairs are parallel to each other, and the upper platform or the lower platform. parallel to the same side.

Further, the steering gear is provided with a plurality of them, which are distributed on the four corners of the opposite side of the upper platform and the lower platform. The steering gear of the upper platform is connected with the first rotating pair at the head end of the branch chain, and the lower platform The steering gear is connected with the second rotating pair at the tail end of the branch chain, the first rotating pair is connected with the third rotating pair through the moving pair, and the third rotating pair is connected with the second rotating pair through the connecting rod.

Further, the moving pair is configured as an electric telescopic rod.

A control method for a mobile parallel mechanism based on the multi-motion mode described above, utilizes the cooperative operation between a plurality of steering gears arranged on an upper platform and a lower platform to control the movement of a plurality of branch chains, and realizes a mobile parallel mechanism. Rolling, Walking and Obstacle Crossing modes and switching between modes.

Further, the rotation of the corresponding first rotation pair and the second rotation pair is controlled by a plurality of the steering gears, and the rotation of the corresponding third rotation pair is driven, thereby controlling the corresponding branch chain to bend and straighten continuously, so as to realize the upper platform and the The alternate landing of the lower platform realizes the rolling mode of the mobile parallel mechanism.

Further, the control method of the scroll mode includes the following steps:

Mark the four steering gears of the upper platform as M1, M2, M3 and M4 in turn, corresponding to the steering gears M1, M2, M3 and M4, and mark the four steering gears of the lower platform as M5, M6, For M7 and M8, the initial state of the rolling mode is set to lock the four moving pairs, the lower platform is on the ground, and the four branches connected to it stand perpendicular to the upper and lower platforms,

Step 1. Control the corresponding second rotating pair to rotate in the rolling direction simultaneously through the steering gears M5, M6, M7 and M8, and drive the corresponding third rotating pair to rotate at the same time, so as to generate an included angle between the corresponding connecting rod and the moving pair, Until the center of gravity of the entire mobile parallel mechanism exceeds the boundary of the lower platform;

Step 2: Control the corresponding first rotating pair to rotate simultaneously in the rolling direction through the steering gears M1, M2, M3 and M4, and drive the corresponding third rotating pair to rotate at the same time, until the corresponding connecting rod and the moving pair are on the same straight line;

Step 3. The first and second rotation pairs controlled by the steering gears M1 and M2 and the steering gears M5 and M6 or the steering gears M3 and M4 and the steering gears M7 and M8 are simultaneously rotated in the rolling direction, so as to drive the steering gears M3 and M8. M4 and steering gears M7, M8 or steering gears M1, M2 and steering gears M5, M6 rotate simultaneously in the rolling direction corresponding to the first rotation pair and the second rotation pair, until the center of gravity of the entire moving parallel mechanism exceeds the center of the upper platform, so that the The upper platform is on the ground, and the four branches connected to it stand perpendicular to the upper platform and the lower platform;

Step 4. Repeat steps 1 to 3 to make the lower platform touch the ground, and the four branches connected to it stand perpendicular to the upper platform and the lower platform;

Step 5: Repeat steps 1 to 4 to make the upper platform and the lower platform land alternately to complete the rolling mode of the mobile parallel mechanism.

Further, in the step 1, the rotation angle of the corresponding second rotation pair controlled by the steering gears M5, M6, M7 and M8 is set to 45 degrees; by the steering gears M1, M2 and the steering gears M5, M6 or the steering gears M3, M4 The first rotation pair and the second rotation pair corresponding to the control of the steering gears M7 and M8 rotate simultaneously in the rolling direction until the angle between the upper platform and the ground is less than 30 degrees.

Further, through the plurality of steering gears arranged on the lower platform, the corresponding second rotation pairs are controlled to rotate at the same time, and the corresponding third rotation pairs and the first rotation pairs are driven to rotate, so that the corresponding connecting rods are connected with the moving pair. Land on the ground to form a four-legged structure, and then control the corresponding third rotating pairs to lift and land one by one through the plurality of steering gears on the lower platform, so as to realize the walking mode of the mobile parallel mechanism; The steering gear controls the corresponding third rotating pair to lift and land one by one, as well as to extend and shorten the corresponding moving pair, so as to realize the obstacle-crossing mode of the mobile parallel mechanism.

Further, the control method of the walking mode includes the following steps:

Mark the four steering gears of the upper platform as M1, M2, M3 and M4 in turn, corresponding to the steering gears M1, M2, M3 and M4, and mark the four steering gears of the lower platform as M5, M6, For M7 and M8, the initial state of the walking mode is set to lock the four moving pairs. The steering gears M5, M6, M7 and M8 control the corresponding second rotating pair to rotate 120 degrees downward at the same time, so that the lower platform is lifted as a whole, and the corresponding connecting Stand on the ground at the connection between the rod and the moving pair, the connection is marked as a, b, c, d in turn, the initial position of the center of gravity of the mobile parallel mechanism is at the geometric center of the mechanism,

Step 1, control the corresponding second rotation pair to turn the set angle on the inner side of the downward platform through the steering gear M5, so that the connection part a moves down the inner side of the platform along the ground, and the connection part b is lifted toward the traveling direction;

Step II: Control the corresponding second rotation pair to rotate downward to the inner side of the platform to set the angle through the steering gear M8, so that the connection point d moves down the inner side of the platform along the ground, and the center of gravity of the moving parallel mechanism exceeds the initial position along the traveling direction, and the connection The place b falls to the ground, and the connection d lifts up;

Step III: Control the corresponding second rotation pair to turn the set angle downwards to the inside of the platform through the steering gear M6, so that the connection b moves down the inner side of the platform along the ground, the connection d falls to the ground, and the connection a lifts up in the direction of travel ;

Step IV, control the corresponding second rotation pair to turn the set angle downwards on the inner side of the platform through the steering gear M7, so that the connection c moves down the inner side of the platform along the ground, and the center of gravity of the moving parallel mechanism exceeds the initial position along the travel direction, and the connection is made. Landing at a, driving the entire mobile parallel mechanism to move in the direction of travel;

Step Ⅴ: Control the corresponding second rotation pair through the steering gears M5, M6, M7 and M8 and simultaneously lower the inner side of the platform to rotate the same set angle, so that the mobile parallel mechanism returns to the initial state;

Step VI, repeat steps I to V, so that the mobile parallel mechanism is always in the walking state.

Further, the control method of the obstacle crossing mode includes the following steps:

Mark the four steering gears of the upper platform as M1, M2, M3 and M4 in turn, corresponding to the steering gears M1, M2, M3 and M4, and mark the four steering gears of the lower platform as M5, M6, M7 and M8, the initial state of obstacle crossing mode is set as the second rotating pair corresponding to the steering gear M5, M6, M7 and M8 control and rotate 120 degrees downward at the same time, so that the lower platform is lifted as a whole, and the corresponding connecting rod is connected with the moving pair Standing on the ground, the connection points are marked as a, b, c, d in turn, and the connection points a and b are close to the obstacle,

Step 1. Control the corresponding second rotation pair to rotate downward to the inner side of the platform through the steering gear M5 to set the angle, so that the connection point a moves down the inner side of the platform along the ground, and the connection point b is lifted up and the corresponding moving pair is shortened. contact with the top of the obstacle;

Step 2. Control the corresponding second rotation pair to rotate downward to the inner side of the platform through the steering gear M6 to set the angle, so that the connection b goes over the obstacle and moves down the inner side of the platform, and the connection a lifts up and moves correspondingly. Vice shortening, over obstacles;

Step iii, the mobile pair corresponding to the connection points a and b are extended to the initial state, and travel according to the traveling mode described in claim 9 until the connection points c and d are close to the obstacle;

Step iv. Control the corresponding second rotation pair to turn the inner side of the platform downward by the set angle through the steering gear M8, so that the connection d moves down the inner side of the platform along the ground, and at the same time, the corresponding moving pair shortens and crosses the obstacle;

Step ⅴ, control the corresponding second rotation pair to rotate downward to the inner side of the platform by the set angle through the steering gear M7, so that the connection c moves down the inner side of the platform along the ground, and at the same time, the corresponding moving pair is shortened and goes over obstacles;

In step ⅶ, the moving pairs corresponding to the connection positions c and d are extended to the initial state, so that the connection positions a, b, c, and d of the mobile parallel mechanism return to the initial state.

The beneficial technical effects of the present invention are:

(1) Collect the symmetrical 4-RRPR multi-mode mobile parallel mechanism as the main body as the mobile mechanism, and use the deformation characteristics of the 4-RRPR mobile parallel mechanism to realize the "full posture" rolling, four-legged walking, obstacle crossing and other motion modes. , avoids the limitation of a single movement mode, has good adaptability, can deal with terrains with typical characteristics such as steps, channels, slopes, etc. with multiple characteristics, and has a wide application prospect;

(2) The 4-RRPR multi-mode mobile parallel mechanism of the present invention performs time-sharing control of each steering gear and motor control through the control circuit board, and the two cooperate with each other to adjust, which can realize the deformation of the mechanism and the relationship between each motion mode. Automatic conversion.

(3) The 4-RRPR multi-mode mobile parallel mechanism of the present invention improves the dynamic performance, increases the structural rigidity, has the characteristics of better rigidity, precision and bearing capacity, and expands the mobile mechanism in the rescue, detection, exploration and other environments. Application range and traffic capacity.

Description of drawings

Fig. 1 is the overall structure schematic diagram 1 of the present invention, and the branched chain is in a bent state;

Fig. 2 is the general structure schematic diagram II of the present invention, and this branch chain is in the elongation state;

3 is a schematic diagram of the change process of the mechanism shape under the rolling mode of the present invention;

Fig. 4 is the initial state schematic diagram of the travel mode of the present invention;

5 is a schematic diagram of the change process of the mechanism shape under the travel mode of the present invention;

6 is a schematic diagram of the change process of the mechanism shape under the obstacle crossing mode of the present invention;

Among them, 1-upper platform, 2-lower platform, 3-branch chain, 31-first rotating pair, 32-second rotating pair, 33-moving pair, 34-third rotating pair, 35-connecting rod, 4- steering gear.

Detailed ways

The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments.

As shown in Figures 1 and 2, the present invention provides a moving parallel mechanism with multi-movement modes, including an upper platform 1 and a lower platform 2 of parallelogram structure, the upper platform 1 and the lower platform 2 are arranged in parallel, and there is a gap between the two. A plurality of branch chains 3 are provided, and the plurality of branch chains 3 are arranged in parallel with each other, including three rotating pairs and one moving pair, the head and tail ends of which are connected with the upper platform 1 and the lower platform 2 through the steering gear 4, and the rotating shafts of all the rotating pairs are connected. The axial centerlines are parallel to each other and parallel to the same side of the upper platform 1 or the lower platform 2 .

There are multiple steering gears 4, which are distributed on the four corners of the opposite side of the upper platform 1 and the lower platform 2. The steering gear 4 of the upper platform 1 is connected to the first rotating pair 31 at the head end of the branch chain 3, and the lower platform The steering gear 4 of 2 is connected with the second rotating pair 32 at the end of the branch chain 3, the first rotating pair 31 is connected with the third rotating pair 34 through the moving pair 33, and the third rotating pair 34 is connected with the second rotating pair 32 through the connecting rod 35. connected. The moving pair 33 can be configured as an electric telescopic rod.

The present invention provides a control method of the mobile parallel mechanism based on the above-mentioned multi-motion mode, which utilizes the time-sharing cooperative operation between the plurality of steering gears 4 arranged on the upper platform 1 and the lower platform 2 to control a plurality of The movement of the branch chain 3, such as bending, straightening, rotating, etc., realizes the switching between the rolling, walking and obstacle-crossing modes of the mobile parallel mechanism and the switching between the modes.

When encountering flat or ditch roads, the entire mechanism can select a "full-stance" rolling mode. The connecting rod 35 can be driven to rotate at a certain angle by driving the steering gear 4 synchronously. Due to the offset of the center of gravity of the mechanism, the mechanism is overturned, and then the steering gear 4 is driven to make the mechanism have a certain acceleration, thereby generating an inertial force to lift the lower platform of the mechanism. , the upper platform is grounded, so that the whole mechanism rolls forward. The rotation of the corresponding first rotation pair 31 and the second rotation pair 32 can be controlled by the plurality of steering gears 4 to drive the rotation of the corresponding third rotation pair 34, so as to control the corresponding branch chain 3 to continuously bend and straighten, so as to realize The alternate landing of the upper platform 1 and the lower platform 2, thereby realizing the rolling of the entire mobile parallel mechanism, as shown in Figure 3, as follows:

Mark the four steering gears 4 of the upper platform 1 as M1, M2, M3 and M4 in turn, corresponding to the steering gears M1, M2, M3 and M4, and mark the four steering gears of the lower platform 2 as M5, M6 in turn , M7 and M8, the initial state of the rolling mode is set to lock the four moving pairs 33, the lower platform 1 is on the ground, and the four branch chains 3 connected to it stand perpendicular to the upper platform 1 and the lower platform 2, as shown in Figure 3 (1) shown,

Step 1. Control the corresponding second rotating pair to rotate simultaneously in the rolling direction through the steering gears M5, M6, M7 and M8. According to the size of the entire mechanism, set the rotation angle such as 45 degrees to drive the corresponding third rotating pair to rotate at the same time. Make an angle between the corresponding connecting rod and the moving pair, as shown in Figure 3(2), until the center of gravity of the entire moving parallel mechanism exceeds the boundary of the lower platform, and the inertial force is generated by the acceleration during the rotation process, and the entire moving parallel mechanism Turn it over, and the connecting rod near the ground touches the ground, as shown in Figure 3(3);

Step 2: Control the corresponding first rotating pair to rotate simultaneously in the rolling direction through the steering gears M1, M2, M3 and M4, and drive the corresponding third rotating pair to rotate at the same time until the corresponding connecting rod and the moving pair are on the same straight line, such as As shown in Figure 3(4);

Step 3. The first and second rotation pairs controlled by the steering gears M1 and M2 and the steering gears M5 and M6 or the steering gears M3 and M4 and the steering gears M7 and M8 are simultaneously rotated in the rolling direction, so as to drive the steering gears M3 and M8. M4 and steering gears M7, M8 or steering gears M1, M2 and steering gears M5, M6 rotate simultaneously in the rolling direction corresponding to the first rotation pair and the second rotation pair, until the angle between the upper platform and the ground is less than 30 degrees, and the entire movement is parallel. The center of gravity of the mechanism exceeds the center of the upper platform, so that the upper platform is on the ground, and the four branch chains connected to it stand perpendicular to the upper platform and the lower platform, as shown in Figure 3(5);

Step 4. Repeat steps 1 to 3 to make the lower platform touch the ground, and the four branches connected to it stand perpendicular to the upper platform and the lower platform;

Step 5: Repeat steps 1 to 4 to make the upper platform and the lower platform land alternately to complete the rolling mode of the mobile parallel mechanism.

When the mechanism is on a flat ground, the mechanism selects the walking mode, and the steering gear can be controlled to synchronously drive the connecting rod to rotate downward by a certain angle, so as to form a state where the four legs are supported on the ground; and then drive the corresponding steering gear respectively to drive the corresponding connecting rods alternately. Raise and land to complete the quadruped walking mode of the mechanism on a flat surface. That is, the corresponding second rotating pair is controlled to rotate at the same time by a plurality of steering gears arranged on the lower platform, which drives the rotation of the corresponding third rotating pair and the first rotating pair, so that the connection between the corresponding connecting rod and the moving pair touches the ground, forming four The foot structure is then controlled by the multiple steering gears on the lower platform to control the corresponding third rotating pair to lift and land one by one to realize the walking of the entire mobile parallel mechanism, as shown in Figures 4 and 5, as follows:

The initial state of the walking mode is set to lock the four moving pairs, the lower platform 1 touches the ground, and the four branch chains 3 connected to it stand perpendicular to the upper platform 1 and the lower platform 2, as shown in Figure 5A, through the steering gear M5, M6, M7 and M8 control the corresponding second rotating pair to rotate 120 degrees downward at the same time, so that the lower platform is lifted up as a whole, and the corresponding connecting rod and the moving pair are standing on the ground, as shown in Figure 5B, the connection is in turn Marked as a, b, c, d, the initial position of the center of gravity of the mobile parallel mechanism is at the geometric center of the mechanism, as shown in Figure 4,

Step 1. Control the corresponding second rotation pair to turn the inner side of the platform downward through the steering gear M5 to set the angle, so that the connection point a moves down the inner side of the platform along the ground, and the center of gravity of the whole mechanism is raised and moved backwards. The connection point acd supports, so that the connection point b is lifted towards the traveling direction, as shown in Figure 5C, the set angle can be designed according to the size of the whole mechanism, such as 15 degrees, and the height h that the connection point can be lifted can be determined as follows calculated by the formula,

h=lsin(α ₁ +α ₂ )-asinα ₂

Wherein, l represents the length of the connecting rod, α ₁ represents the rotation angle of the second rotating pair corresponding to the steering gear control, and α ₂ represents the angle between the connecting rod and the ground;

Step II: Control the corresponding second rotation pair to rotate downward to the inner side of the platform through the steering gear M8 to set the angle, so that the connection d moves down the inner side of the platform along the ground, and the center of gravity of the moving parallel mechanism exceeds the initial position along the traveling direction, and the connection Landing at point b, the whole mechanism moves forward and is supported by the connection point abc, and the connection point d lifts up, as shown in Figure 5D;

Step III: Control the corresponding second rotation pair to turn the inner side of the platform downward through the set angle through the steering gear M6, so that the connection b moves down the inner side of the platform along the ground, the connection d falls to the ground, and the center of gravity of the whole mechanism moves backward, Supported by the connection point bcd, the connection point a is lifted towards the traveling direction, as shown in Figure 5E;

Step Ⅳ. Control the corresponding second rotation pair to turn the inner side of the platform downward through the steering gear M7 to set the angle, so that the connection point c moves down the inner side of the platform along the ground, and the center of gravity of the moving parallel mechanism exceeds the initial position along the traveling direction, and the connection is Landing at a, drives the entire mobile parallel mechanism to move in the direction of travel, as shown in Figure 5F, the travel distance L at this time can be calculated by the following formula:

L=lcos(α ₁ +α ₂ )-acosα ₂

Wherein, l represents the length of the connecting rod, α ₁ represents the rotation angle of the second rotating pair corresponding to the steering gear control, and α ₂ represents the angle between the connecting rod and the ground;

Step Ⅴ: Control the corresponding second rotation pair through the steering gears M5, M6, M7 and M8 and simultaneously lower the inner side of the platform to rotate the same set angle, so that the mobile parallel mechanism returns to the initial state;

Step VI, repeat steps I to V, so that the mobile parallel mechanism is always in the walking state.

When the mechanism is on uneven ground, the mechanism selects the four-legged walking obstacle mode, and the steering gear can be controlled to synchronously drive the connecting rod to rotate downward at a certain angle, so as to form a state where the four feet are supported on the ground; and then drive the corresponding steering gear to drive the The corresponding connecting rods are lifted alternately, and the corresponding linear motors are controlled to drive the connecting rods to cross the obstacles, so as to complete the four-legged obstacle-crossing mode of the mechanism on uneven roads. That is, the corresponding second rotating pair is controlled to rotate at the same time by a plurality of steering gears arranged on the lower platform, which drives the rotation of the corresponding third rotating pair and the first rotating pair, so that the connection between the corresponding connecting rod and the moving pair touches the ground, forming four The foot structure is then controlled by the multiple steering gears on the lower platform to control the corresponding third rotating pair to lift and land one by one, as well as the extension and shortening of the corresponding moving pair, so as to realize the obstacle crossing of the entire mobile parallel mechanism. The details are as follows:

The initial state of the obstacle crossing mode is set as the second rotating pair corresponding to the steering gear M5, M6, M7 and M8 control and rotate 120 degrees downward at the same time, so that the lower platform is lifted as a whole, and the corresponding connecting rod and the moving pair are connected to the ground and stand. The joints are marked as a, b, c, and d in turn, and the joints a and b are close to the obstacle, as shown in Figure 6(A),

Step 1. Control the corresponding second rotation pair to rotate downward to the inner side of the platform through the steering gear M5 to set the angle, so that the connection point a moves down the inner side of the platform along the ground, and the connection point b is lifted up and the corresponding moving pair is shortened. Contact with the top of the obstacle, and the end of the connecting rod corresponding to the connection b has exceeded the top edge of the obstacle, as shown in Figure 6(B);

Step 2. Control the corresponding second rotation pair to rotate downward to the inner side of the platform through the steering gear M6 to set the angle, so that the connection b goes over the obstacle and moves down the inner side of the platform, and the connection a lifts up and moves correspondingly. The pair shortens and crosses the obstacle, as shown in Figure 6(C);

Step iii, the mobile pair corresponding to the connection points a and b are extended to the initial state, as shown in Figure 6(D), as shown in the traveling mode according to claim 9, until the connection points c and d are close to the obstacle;

Step iv. Control the corresponding second rotation pair to turn down the inner side of the platform through the steering gear M8 to set the angle, so that the connection d moves down the inner side of the platform along the ground, and at the same time, the corresponding moving pair is shortened and crosses the obstacle, as shown in the figure 6(E);

Step ⅴ, control the corresponding second rotation pair to turn down the inner side of the platform through the steering gear M7 to set the angle, so that the connection c moves down the inner side of the platform along the ground, and at the same time, the corresponding moving pair is shortened and crosses the obstacle, as shown in the figure 6(F);

In step ⅶ, the moving pairs corresponding to the connection points c and d are extended to the initial state, so that the connection points a, b, c, and d of the mobile parallel mechanism return to the initial state.

Although the specific embodiments of the present invention have been described above, those skilled in the art should understand that these are only examples, and various changes may be made to these embodiments without departing from the principle and essence of the present invention. Modifications, therefore, the scope of protection of the present invention is defined by the appended claims.

Claims (7)

1. A moving parallel mechanism with multiple motion modes is characterized in that: the device comprises an upper platform and a lower platform which are of parallelogram structures, wherein the upper platform and the lower platform are arranged in parallel, a plurality of branched chains are arranged between the upper platform and the lower platform, the branched chains are arranged in parallel, the branched chains comprise three revolute pairs and a revolute pair, the head end and the tail end of the revolute pair are connected with the upper platform and the lower platform through steering engines, and the axial center lines of the rotating shafts of all the revolute pairs are parallel to each other and are parallel to the same side of the upper platform or the lower platform;

the steering gears are distributed on four corners of one surface of the upper platform opposite to the lower platform, the steering gears of the upper platform are connected with a first rotating pair at the head end of the branched chain, the steering gears of the lower platform are connected with a second rotating pair at the tail end of the branched chain, the first rotating pair is connected with a third rotating pair through a moving pair, and the third rotating pair is connected with the second rotating pair through a connecting rod;

the movement of a plurality of branched chains is controlled by utilizing the cooperative operation between a plurality of steering engines arranged on the upper platform and the lower platform, so that the rolling, walking and obstacle crossing modes of the movable parallel mechanism and the switching between the modes are realized;

the steering engines arranged on the lower platform control the corresponding second revolute pairs to rotate simultaneously to drive the corresponding third revolute pairs and first revolute pairs to rotate, so that the joints of the corresponding connecting rods and the revolute pairs land to form a four-footed structure, and the steering engines on the lower platform control the corresponding third revolute pairs to lift up and land one by one to realize a walking mode of the movable parallel mechanism; and controlling the corresponding third revolute pairs to lift up and fall to the ground one by one and to extend and shorten corresponding revolute pairs through a plurality of steering engines on the lower platform, so as to realize an obstacle crossing mode of the movable parallel mechanism.

2. The multiple motion mode mobile parallel mechanism of claim 1, wherein: the sliding pair is an electric telescopic rod.

3. The multiple motion mode mobile parallel mechanism of claim 1, wherein: the steering engines are used for controlling the corresponding first rotating pair and the corresponding second rotating pair to rotate so as to drive the corresponding third rotating pair to rotate, so that the corresponding branched chains are controlled to be continuously bent and straightened, the upper platform and the lower platform are alternatively landed, and the rolling mode of the movable parallel mechanism is further realized.

4. A multiple movement pattern moving parallel mechanism according to claim 3, wherein the control method of the rolling pattern includes the steps of:

the four steering engines of the upper platform are sequentially marked as M1, M2, M3 and M4 in sequence, the four steering engines of the lower platform are sequentially marked as M1, M2, M3 and M4, the four steering engines of the lower platform are sequentially marked as M5, M6, M7 and M8, the initial state of the rolling mode is set to be four sliding pairs, the lower platform lands on the ground, four branched chains connected with the lower platform stand perpendicular to the upper platform and the lower platform,

step one, controlling the corresponding second rotating pairs to simultaneously rotate in the rolling direction through the steering engines M5, M6, M7 and M8, driving the corresponding third rotating pairs to simultaneously rotate, and enabling the corresponding connecting rods and the moving pairs to form included angles until the gravity center of the whole moving parallel mechanism exceeds the boundary of the lower platform;

step two, controlling the corresponding first rotating pairs to simultaneously rotate in the rolling direction through the steering engines M1, M2, M3 and M4, and driving the corresponding third rotating pairs to simultaneously rotate until the corresponding connecting rods and the corresponding sliding pairs are positioned on the same straight line;

step three, controlling corresponding first rotating pairs and second rotating pairs to simultaneously rotate in the rolling direction through steering engines M1, M2 and steering engines M5, M6 or steering engines M3, M4 and steering engines M7, M8, driving the steering engines M3, M4 and the steering engines M7, M8 or the steering engines M1, M2 and the steering engines M5, M6 to simultaneously rotate in the rolling direction corresponding to the first rotating pairs and the second rotating pairs until the gravity center of the whole moving parallel mechanism exceeds the center of the upper platform, so that the upper platform lands, and four branched chains connected with the upper platform stand perpendicular to the upper platform and the lower platform;

step four, repeating the steps one to three, so that the lower platform lands on the ground, and four branched chains connected with the lower platform stand vertically to the upper platform and the lower platform;

and step five, repeating the steps one to four to enable the upper platform and the lower platform to touch the ground alternately to complete the rolling mode of the movable parallel mechanism.

5. The multiple motion mode mobile parallel mechanism of claim 4, wherein: in the first step, the steering engines M5, M6, M7 and M8 are used for controlling the rotation angle of the corresponding second revolute pair to be set to 45 degrees; the corresponding first rotating pair and the corresponding second rotating pair are controlled to rotate simultaneously in the rolling direction through the steering engines M1 and M2 and the steering engines M5 and M6 or the steering engines M3 and M4 and the steering engines M7 and M8 until the included angle between the upper platform and the ground is less than 30 degrees.

6. The multiple movement pattern mobile parallel mechanism according to claim 1, wherein the control method of the walking pattern comprises the steps of:

sequentially marking four steering engines of the upper platform as M1, M2, M3 and M4 in a clockwise manner, corresponding to the steering engines M1, M2, M3 and M4, sequentially marking the four steering engines of the lower platform as M5, M6, M7 and M8, setting the initial state of a walking mode to be four moving pairs in a locked manner, controlling the corresponding second rotating pairs to rotate downwards by 120 degrees by the steering engines M5, M6, M7 and M8, so that the lower platform is integrally lifted, the joints of the corresponding connecting rods and the moving pairs are grounded and stand, sequentially marking the joints as a, b, c and d, and the initial position of the gravity center of the moving parallel mechanism is positioned at the geometric center of the mechanism,

step I, controlling a corresponding second revolute pair to rotate towards the inner side of the lower platform by a set angle through a steering engine M5, enabling a joint a to move towards the inner side of the lower platform along the ground, and enabling a joint b to lift towards the advancing direction;

step II, controlling a corresponding second revolute pair to rotate towards the inner side of the lower platform by a set angle through a steering engine M8, enabling a joint d to move towards the inner side of the lower platform along the ground, moving the gravity center of the parallel mechanism to exceed the initial position along the advancing direction, enabling a joint b to fall to the ground, and lifting the joint d;

step III, controlling a corresponding second revolute pair to rotate towards the inner side of the lower platform by a set angle through a steering engine M6, enabling a joint b to move towards the inner side of the lower platform along the ground, enabling a joint d to land, and lifting the joint a towards the traveling direction;

step IV, controlling a corresponding second revolute pair to rotate towards the inner side of the lower platform by a set angle through a steering engine M7, enabling a joint c to move towards the inner side of the lower platform along the ground, moving the gravity center of the parallel mechanism to exceed the initial position along the advancing direction, and enabling a joint a to land to drive the whole movable parallel mechanism to move towards the advancing direction;

step V, controlling corresponding second revolute pairs through steering engines M5, M6, M7 and M8, and enabling the inner sides of the lower platforms to rotate by the same set angle at the same time, so that the movable parallel mechanism returns to the initial state;

and VI, repeating the steps I to V to enable the movable parallel mechanism to be in a walking state all the time.

7. The multiple-motion-mode mobile parallel mechanism according to claim 6, wherein the control method of the obstacle crossing mode comprises the steps of:

the four steering engines of the upper platform are sequentially marked as M1, M2, M3 and M4 in a clockwise manner, the four steering engines of the lower platform are correspondingly marked as M1, M2, M3 and M4 in a clockwise manner, the four steering engines of the lower platform are sequentially marked as M5, M6, M7 and M8 in a clockwise manner, the initial state of the obstacle crossing mode is set as that the steering engines M5, M6, M7 and M8 control the corresponding second revolute pair to rotate downwards by 120 degrees at the same time, so that the lower platform is integrally lifted, the corresponding connecting rod and the moving pair are connected with the ground and stand, the connecting positions are sequentially marked as a, b, c and d, and the connecting positions a and b are close to an obstacle,

step i, controlling a corresponding second revolute pair to rotate towards the inner side of the lower platform by a set angle through a steering engine M5, enabling a joint a to move towards the inner side of the lower platform along the ground, and lifting a joint b upwards while shortening a corresponding revolute pair to contact the top of the barrier;

step ii, the steering engine M6 is used for controlling the corresponding second revolute pair to rotate towards the inner side of the lower platform by a set angle, so that the joint b crosses the obstacle and moves towards the inner side of the lower platform along the ground, the joint a is lifted upwards, and meanwhile, the corresponding revolute pair is shortened to cross the obstacle;

step iii, extending the sliding pair corresponding to the joints a and b to an initial state, and advancing according to the advancing mode of claim 6 until the joints c and d are close to the obstacle;

step iv, controlling the corresponding second revolute pair to rotate towards the inner side of the lower platform by a set angle through a steering engine M8, so that the joint d moves towards the inner side of the lower platform along the ground, and meanwhile, the corresponding revolute pair is shortened to cross an obstacle;

step v, controlling the corresponding second revolute pair to rotate towards the inner side of the lower platform by a set angle through a steering engine M7, so that the joint c moves towards the inner side of the lower platform along the ground, and meanwhile, the corresponding revolute pair is shortened to cross an obstacle;

and step vii, extending the sliding pair corresponding to the joints c and d to the initial state, so as to restore the joints a, b, c and d of the movable parallel mechanism to the initial state.

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